As a writer, JRR Tolkien is often a master of understatement. Very frequently, he speaks of Middle Earth objectively, like a historian. He doesn't try to "sell" Middle Earth to the reader, he just tells the reader about the events that took place there, and takes no responsibility when the reader inevitably falls in love with his imaginary world. Like Gandalf introducing his adventuring party of 13 dwarves to Beorn, Tolkien can mention something big as just an after-thought, which, to a reader already enamored by the world of hobbits and dwarves and elves and wizards, can have the effect of disguising some surprisingly dark truths about Middle Earth.
Some things in Tolkien's legendarium are overlooked because there's a lack of exposition in the books published. Galadriel is a prime example. Ask any Tolkien nerd what the deal with Galadriel is, and they'll tell you that she's stunningly powerful. First of all, she's really old, so she's had lots of time to perfect her various skills, and also to grow wiser than some pretty famously wise Eldar. From Unfinished Tales of Numenor and Middle-earth:
Galadriel was the greatest of the Noldor, except Feanor maybe, though she was wiser than he, and her wisdom increased with the long years. [Unfinished Tales of Numenor and Middle-earth]
She's the owner of Nenya, a Ring of Power. She protects the Elven woods, and is considered a sorceress by Gimli.
One of the things the Rings of Power TV show does well, I think, is reflect her skill as a learnèd and masterful warrior.
...she was strong of body, mind, and will, a match for both the loremasters and the athletes of the Eldar in the days of their youth. [Unfinished Tales of Numenor and Middle-earth]
It was her hair that gave Feanor the idea to create the Silmarils:
her hair was held a marvel unmatched. It was golden like the hair of her father and of her foremother Indis, but richer and more radiant, for its gold was touched by some memory of the starlike silver of her mother; and the Eldar said that the light of the Two Trees, Laurelin and Telperion, had been snared in her tresses. Many thought that this saying first gave to Feanor the thought of imprisoning and blending the light of the Trees that later took shape in his hands as the Silmarils. [Unfinished Tales of Numenor and Middle-earth]
In other words, she was around before the Silmarils even existed.
The problem, insofar as there is a problem, is that we don't "see" any of this for ourselves. We're told about it in a posthumous publication, and as willing as I am to accept it, I still lack an emotional connection to it. This is what I enjoyed about Rings of Power. I got to see and experience what Galadriel hinted at when she warned Frodo that she must not take possession of the One Ring.
Unlike the scope of Galadriel's true power, some things in Middle-earth we overlook because, I think, we're all accustomed to Tolkien's world such that we take things for granted. The very existence of orcs became a fantasy trope, so it doesn't really disturb us much when orcs invade Middle-earth. The presence of giant spiders seems quaint to modern cinema-goers who've seen their heroes fight aliens with acid for blood, or demons, or formless tentacled aberrations.
As with the physical threats of Middle-earth, Tolkien doesn't overstate the danger of the One Ring. I think many of us miss it because the One Ring is the titular threat. If you know about the book series called Lord of the Rings then you know there's a ring. It can be easy to overlook the hidden and almost absolute power of this simple magical item.
The Ring's obvious power is its ability to make its wearer invisible. That's a useful trick, but it's also a little suspect. A ring that makes you stronger or faster is overt, but a ring of invisibility is inherently deceitful. Used under the right conditions, it can be justified, but it's obviously ripe for abuse.
Invisibility, of course, is the Ring's secondary ability. That's not its true purpose. But its invisibility is how we're introduced to the Ring, both in The Hobbit and in Lord of the Rings. Tolkien sells the reader on the idea that the Ring is primarily a ring of invisibility, with a minor flaw. Something to do with a dark lord and world domination, or whatever, but anyway watch what happens when you put it in fire! You can see an inscription on it! That's so peculiar. And have I mentioned it makes you invisible when you put it on?
The most sobering and horrifying aspect of the One Ring is that it corrupts without consent. Many of the characters we see bearing the Ring are eventually told about its hidden power, and so they are able to struggle with the morality of wearing it at all. But imagine if Bilbo had found the Ring, slipped it on, wandered out of Gollum's cavern, and just kept walking until he'd gotten back to the Shire? Suppose Gandalf assumed he'd been lost to the goblins, never knowing that the Ring had been uncovered. Bilbo's fate, with no warning of the Ring's power, would have been completely different.
Imagine finding the Ring yourself (were you alive in Middle-earth, I mean). With no one to tell you of its corrupting influence, you'd be under the control of Sauron in no time. There's no saving throw or Will save against the Ring. As long as you possess it, the Ring corrupts.
Forget free will, philosophy, and ethics. There's no negotiation or meaningful struggle. The Ring wins in the end.
It's one of the bleakest curses in all of fantasy. It's almost Lovecraftian, in the sense that a mere mortal has no hope against a primordial force.
I don't see the Ring as a metaphor, partly because Tolkien says as much in his letters but also because it doesn't read like one to me. I don't see the Ring as "sin" or xenophobia or industrialization or addiction or whatever else people have compared it to over the decades (although it may share attributes with those things.) It's just a deceitful and evil force in a fantasy world with the power to trick an unsuspecting person into picking it up and becoming its eternal slave.
No wizard can counteract the Ring's spell. There's no cleric in this world who can pray its evil away. And once you're corrupted, there's no Greater Restoration spell to get you back. You're consumed by it, forever, no matter what.
Even more horrifyingly, the Ring is just one tiny piece of jewelry with a fraction of all possible evil imbued within it. Far from being the actual threat of the Lord of the Rings, the Ring is actually only a harbinger. So much more evil is possible.
I was talking to a friend about Alfred Hitchcock's Birds recently, and she recalled with horror the first time she saw the shot of the corpse whose eyes had been eaten out of his skull. There's no music, no gimmicks. It's just a cold and stark shot of a dead man in a mostly common setting, with his eyes missing.
I think that's Tolkien's take on the One Ring. The Ring doesn't get ominous background music when you first see it, it doesn't make you feel ill at ease but it also doesn't make you feel particularly delighted. It's just a plain ring. Could be good to pawn it off for a few dollars, or maybe just keep it because it's probably hardly worth the trouble. It's magic, which is intriguing, but then again in Middle-earth there are magic purses that cry out when they're being stolen and swords that glow when enemies are near. A little magic is as exciting as winning a lottery without a cash prize.
Tolkien understates the threat in Lord of the Rings because instead of telling us about it, he chooses to demonstrate the Ring's power. We see it chiefly in Gollum, who Tolkien mercifully makes a little twisted from the start. But we do eventually start to see hints of corruption in Bilbo and even Frodo, who we know and love, and who we don't want to be unwillingly corrupted.
Tolkien's world has its moments of extreme darkness, and I think it can take its audience by surprise, but it's always there. You don't have to ponder the Ring to feel its threat against the serenity of Middle-earth, or the relief offered by the heroes brave enough to stand against it.